Growing herbs: the complete cold-climate guide

Growing herbs at a glance

Contents

• Growing herbs at a glance
• Annual, biennial and perennial herbs
• Mediterranean herbs or leafy herbs?
• Why can't you grow all herbs in one pot?
• Comparison table: 16 herbs from seed to harvest
• Seed, plug or plant?
• Pots, beds or a herb spiral?
• Soil and drainage: two mixes cover everything
• How much sun and water do herbs need?
• Feeding – and why too much nitrogen ruins the flavour
• Pinching and pruning that keeps plants bushy
• What time of day should you harvest herbs?
• Drying, freezing and herb salt
• Mint that runs – how to keep it in bounds
• Why do cilantro and dill bolt so fast?
• Overwintering perennial herbs in zones 3–6
• Zone table: sowing, planting out and winter care
• Common mistakes
• Frequently asked questions

Annual, biennial and perennial herbs

Annuals

Basil, dill, cilantro, chervil and marjoram germinate, flower, set seed and die within one season. Seed is their only goal, and your job is to stop them: once flower stalks rise, dill turns stringy, cilantro bitter and basil loses its sweetness. So they get sown in succession, fed more than the perennials, pinched hard – and pulled in October.

Biennials

Parsley and caraway build leaf in year one and flower in year two, so you get one good leaf year. Sow fresh parsley every year, and in zones 3 and 4 treat it as an annual since it rarely overwinters.

Perennials

Chives, mint, thyme, oregano, sage, tarragon, lemon balm, lovage and lavender come back year after year, and the logic reverses. The goal is not leaf this season but a plant that survives winter: lean soil, sparing feed, cutting stopped early.

The woody ones – rosemary, thyme, sage, lavender and winter savory – build wood that does not resprout, so cutting into grey stems leaves a permanent hole.

Mediterranean herbs or leafy herbs?

The second grouping is even more practical: every culinary herb sits in one of two camps, and the camps want opposite things.

Mediterranean herbs: rosemary, thyme, oregano, sage, lavender

They grow wild on dry, stony, sun-baked slopes in thin alkaline soil. The leaves are small, hairy or leathery and loaded with the essential oils that stop them drying out – and those oils are what you want in the kitchen.

They need lean soil, sharp drainage, full sun and dry spells between waterings. What kills them is wet soil combined with cold, heavy clay, and fertiliser. Give sage rich soil and nitrogen and it grows fast and floppy and will not survive winter. A rosemary in wet soil in November is dead by February – root rot, not cold.

Leafy herbs: basil, parsley, dill, cilantro, chives, mint

These come from damp meadows, stream banks and cultivated ground. The leaves are large, soft and thin, and that mass needs both water and nutrients, with midday shade welcome. What kills them is drought: a basil that has wilted once never fully recovers, and dry soil is the fastest route to bolting.

Why can't you grow all herbs in one pot?

The mixed herb planter sold in spring looks wonderful in June and is dead by August, because one pot can only have one watering schedule.

Put basil and rosemary together and you must choose. Water for the basil and the rosemary's roots stay permanently damp and it rots from the inside; water for the rosemary and the basil wilts every other day. The same conflict sits in the mix: rosemary wants 25 percent grit, basil wants compost.

Groupings that work

• The dry pot. Thyme, oregano, sage and winter savory in a lean, gritty mix, 10 litres (2.5 gal), full sun.
• The moist pot. Parsley, chives and chervil in fertile compost, evenly damp.
• Its own pot. Mint because it runs, rosemary because it comes indoors, basil because it wants heat.

If you still want one container, drop individual pots inside a larger outer one: it reads as a single planting, but each plant has its own mix and watering. The thinking is the same as in companion planting – neighbour is not roommate.

Comparison table: 16 herbs from seed to harvest

The hardiness column is for ground-planted herbs in well-drained soil; a wet or windswept site behaves like one zone colder. "Tender" means the plant comes indoors everywhere in zones 3–6.

Read down the columns: every lean-soil herb also wants full sun, and every "fertile, moist" herb tolerates part shade.

Seed, plug or plant?

Buy a plant

The right call for anything perennial and woody. Rosemary, lavender, sage and thyme germinate slowly and unevenly, and one plant stands for ten years. French tarragon – the one with real flavour – sets no viable seed and comes only from division, as do most named mints.

Start indoors

The right call for basil, parsley, oregano, lemon balm and thyme. Sow in seed compost 6–8 weeks before planting out: late February in zone 6, early April in zone 3. Thyme, oregano and lemon balm need light to germinate – press the seed onto the surface instead of covering it, while basil and parsley get 5 mm (1/4 in) of cover.

Light is the limiting factor: a windowsill in March is not enough, so a lamp 10–15 cm (4–6 in) above the seedlings for 14–16 hours a day changes everything. The guide to starting seeds indoors covers the lighting setup. Harden the plants off over one to two weeks – basil taken straight into full May sun scorches.

Direct sow

The right call for dill, cilantro, chervil, borage and caraway. All have a long taproot that resents moving, and a transplanted dill bolts at once.

Sow once soil reaches 10 °C (50 °F): mid-April in zone 6, late May in zone 3. Depth 1–1.5 cm (1/2 in), rows 20–25 cm (8–10 in) apart, thinned to 8–10 cm (3–4 in). The succession matters most: a new short row every two to three weeks gives leaf all season instead of a wall of dill for three weeks. A seed sowing calendar makes that easy to plan.

Pots, beds or a herb spiral?

Pots

Containers win on three counts: you control the mix, you can chase the sun, and you can bring in what is not hardy. For Mediterranean herbs in a cold, wet climate a pot often beats open ground, because you avoid a winter of soaked soil.

At least 3 litres (1 US gal) per leafy herb, 8–10 litres (2–2.5 gal) for rosemary and sage, 10 litres or more for mint and lovage. Depth beats width for parsley and cilantro, and terracotta dries faster than plastic – good for Mediterranean herbs, a problem for basil.

Beds

In the ground, perennials get real root depth and end up far hardier than in a pot, because the rootball does not freeze through. Chives, mint, lovage, oregano and thyme belong in soil, in a bed of their own rather than the vegetable plot, since they should not be dug over every spring. A raised bed works especially well: better drainage, earlier warmth, and a lean mix even over clay. The guide to the best raised bed crops covers the pairings.

Herb spiral

A herb spiral solves the grouping problem with geometry instead of scheduling. Build a spiral of stone or brick, 1.5–2 m (5–6 ft) across, rising from ground level at the outside to 0.8–1 m (2.5–3 ft) at the centre, with coarse rubble at the base and lean mix at the top.

That gives four microclimates in 2 sq m (20 sq ft): rosemary, thyme and winter savory at the top where soil is thin, oregano, sage and lavender below them, then chives and tarragon, and at the bottom on the north side where water collects, parsley, chervil and mint. The south face runs several degrees warmer than the north, enough to carry thyme through a winter it would not otherwise survive.

Soil and drainage: two mixes cover everything

Two mixes cover every herb in this guide.

Lean mix for Mediterranean herbs

Three parts loam-based potting compost to one part coarse grit, 2–6 mm. That is 25 percent grit by volume, matching the RHS recommendation of up to 25 percent coarse grit or perlite in a compost such as John Innes No. 1 – No. 3 for larger perennials like rosemary and sage. Add garden lime if your compost is acid; lavender, thyme and sage want pH 6.5–7.5.

Fertile mix for leafy herbs

Potting compost with 10–20 percent well-rotted garden compost, no grit. It has to hold moisture, and coir or vermiculite evens out the drying.

Drainage in practice

Use coarse grit, not fine sand, which packs down with clay. On clay soil raise the bed 15–20 cm (6–8 in) rather than digging grit into a hole, which only creates a sump. Gravel in the base of a pot does nothing either. What works is drainage holes, a gritty mix all through, and pot feet.

How much sun and water do herbs need?

Light

Six hours of direct sun is the floor for nearly every culinary herb, and Mediterranean herbs want eight. Light is the raw material for essential oils, and a thyme in part shade is noticeably less fragrant. Parsley, chervil, chives and mint manage on four to five.

Indoors you need a lamp. A south window works in June and not in November – which is why supermarket herb pots die in fall. Count on 12 hours of artificial light a day, as University of Minnesota Extension advises. The tell for too little light is bare stem between the leaf pairs.

Watering, two different answers

Mediterranean herbs get water only once the compost is dry 2–3 cm (1 in) down. Water until it runs from the base, then wait – roughly every five to seven days in July in a pot, far less often in May and September.

Leafy herbs must never dry out completely; check with a finger 5 mm below the surface, and expect a basil in a 3-litre pot in full sun to need water daily in heat. In the ground one thorough soaking a week beats daily sips – University of Minnesota Extension recommends watering deeply to 20 cm (8 in).

Water in the morning, at soil level – leaves that stay wet overnight bring mildew on mint and grey mould on basil. A 3–5 cm (1–2 in) mulch halves the demand for leafy herbs, but keep it off the stem bases of Mediterranean herbs.

Feeding – and why too much nitrogen ruins the flavour

This is where most growers go wrong, and the error is generosity: herbs are the one group where less feed gives a better result.

The mechanism

Nitrogen drives leaf growth: the plant builds large, thin, water-filled cells and favours volume over chemistry, while essential oils form when it has light and time but no surplus. Iowa State University Extension puts it plainly – high soil fertility gives lush growth but reduced essential oil production. The surplus also costs hardiness, since late, fast shoots are unripened when frost arrives.

Rates that work

• Perennials in the ground. One dressing of balanced fertiliser in spring, about 30 g per sq m (1 oz per sq yd) – University of Minnesota gives 85 g of 5-10-5 per 3 m (3 oz per 10 ft) of row. Nothing after that.
• Annual leafy herbs. Base-dress with compost, then a top-up in July if growth stalls.
• Containers. Nutrients leach out within weeks. Half-strength liquid feed every three to four weeks outdoors, every six weeks indoors.
• Mediterranean herbs in pots. Half strength once or twice all summer.

The stop date matters more than the dose: feed no perennial herb after mid-July.

Pinching and pruning that keeps plants bushy

A herb that is never cut grows tall, leggy and bare at the base. Cutting is shaping, and it starts long before you need the leaves.

Pinching annuals

Pinch out the tip as soon as the plant has three or four leaf pairs, at about 15 cm (6 in), just above a pair. Each cut gives two new shoots – three pinches turn one stem into eight. The technique is covered in the guide to growing basil. Flower buds come off immediately on anything grown for leaf.

Pruning perennials

Herbaceous perennials take rough treatment: cut the whole plant to 5 cm (2 in) when it looks tired in July and it returns with fresh leaf in three weeks. Chives take three cuts a season.

Woody perennials are fragile. Two rules: never cut into the grey wood, and never take more than a third of the top growth at once – Iowa State University Extension gives that third as the ceiling. Do it in April, when new shoots show what is alive. A lavender cut back by a third each April makes a tight mound instead of a hollow bush. More in the guide to growing lavender.

What time of day should you harvest herbs?

Mid-morning, once the dew has dried but before the sun is high. Oil content peaks then and falls measurably in the day's heat – Iowa State University Extension points to that window.

Flavour also peaks as flower buds appear but before they open, so one big cut in early July often yields more than several later ones.

How much at a time

• Annuals. Cut back to 10–15 cm (4–6 in); the plant regrows for one to three cuts a season.
• Perennials. No more than a third of the top growth.
• Chives. Cut the whole clump 3–5 cm (1–2 in) above the soil, not the tips – tipped leaves turn into yellow points all season.
• Parsley. Outer stems at the base, never the crown.

Stop cutting perennials by mid-August, since every cut starts shoots that will freeze. Annuals you crop until the first hard frost.

Drying, freezing and herb salt

Dry small, tough, oil-rich leaves; freeze large, soft ones.

Air drying

Best for thyme, oregano, sage, rosemary, marjoram, savory and lavender. Bundle four or five stems and hang them upside down somewhere warm, airy and dark. University of Minnesota Extension allows 7–14 days, Iowa State 2–4 weeks at 20–27 °C (70–80 °F). A thick bunch moulds from the inside.

A dehydrator at 35–46 °C (95–115 °F) for 2–6 hours is quicker and keeps the colour; an oven works only on its lowest setting with the door ajar. It is done when the leaves crumble but the stems still bend. Store leaves whole and crush at the stove – a whole leaf keeps its oils far longer than powder. Airtight jar, cool and dark, one year.

Freezing

Best for basil, dill, parsley, chives, cilantro, mint and tarragon, which turn to tasteless hay when dried. Three methods:

1. Whole leaves in a bag. Rinse, dry thoroughly, lay flat in a freezer bag; they crumble straight from frozen.
2. Ice cubes. Chop, fill the tray two thirds full, top with water or olive oil and freeze. One cube is roughly a tablespoon of chopped herb, and oil protects against freezer burn.
3. Herb butter. Beat chopped herbs into soft butter, roll in film and freeze.

Use frozen herbs within a year, and never thaw them.

Herb salt

Four parts coarse salt to one part fresh, finely chopped herb by weight. Blitz together, spread thinly on parchment and leave at room temperature for a couple of days, or in an oven at 50 °C (120 °F) with the door ajar. Sage and rosemary suit potatoes, dill and chives fish, oregano and thyme tomato sauce. Herb salt keeps a year and loses far less aroma than dried leaf, because the salt binds the oils.

Mint that runs – how to keep it in bounds

Mint spreads by underground runners just below the surface. One mint plant in a border is a mint border after three years, and the RHS recommends growing it in a container for that reason.

• A free-standing pot. 10 litres (2.5 gal) or more, its own compost, no contact with the ground.
• A sunk pot. Bury a bottomless pot or a length of pipe so the rim stands 5 cm (2 in) above soil level – runners climb over a rim that is flush.
• A root barrier. Edging sunk 30 cm (12 in) around the patch.

Mint in a pot is root-bound within two years. Lift the clump every second spring, split it with a spade, discard two thirds and replant the healthiest piece in fresh compost. Mint is also the one herb here that wants rich compost and steady moisture. Keep cultivars apart – peppermint, spearmint and the flavoured sorts hybridise.

Why do cilantro and dill bolt so fast?

Both are annuals programmed to set seed fast. Bolting is the plant's plan, not a fault, and three things speed it up: heat, drought and root disturbance.

Cilantro

Cilantro is a cool-season crop. Above 25 °C (77 °F) it throws a flower stalk almost regardless of care, and the leaves narrow and turn bitter at the same time.

• Direct sow, never transplant. A disturbed taproot means a flower stalk in two weeks.
• Sow in succession. Penn State Extension recommends fresh seed every two to four weeks.
• Afternoon shade in July. Site the row where it is shaded late in the day.
• Slow-bolt cultivars. 'Slow Bolt', 'Leisure' and 'Santo' are bred for it, and 'Calypso' bolts about three weeks later than 'Santo'.
• Steady moisture. Drought triggers bolting, so mulch helps.

Space plants 15–20 cm (6–8 in) apart. If it bolts anyway, leave it: green immature seed is excellent in food, and ripe dried seed is the spice coriander – cut whole stems once the seed yellows and finish drying in a paper bag.

Dill

Dill bolts as days lengthen. Sow thickly and thin only moderately; a dill standing alone bolts sooner than one in a row. Harvest from 20 cm (8 in) tall, cutting whole tops, and sow again every two weeks. 'Fernleaf' is compact and slow to bolt, best for pots and leaf, while tall sorts such as 'Bouquet' are bred for seed heads and flower fast by design.

Overwintering perennial herbs in zones 3–6

Perennial herbs rarely die of cold alone. They die of wet soil combined with cold, of bare frost without snow, and of being cut back in fall.

• Do not cut woody herbs back. The top growth shelters the crown, and a cut made in October does not heal. All pruning waits for April.
• Do cut herbaceous perennials back. Mint, lemon balm, lovage and chives die down anyway; clear the old growth in late winter.
• Mulch after the ground freezes, not before. University of Minnesota Extension gives 5–13 cm (2–5 in) of straw, compost or leaves, to stop the thaw-refreeze cycle.
• A pot is colder than the ground. A container outdoors freezes right through the rootball – count on two zones less hardiness. Sink it, move it to an unheated garage, or wrap it in bubble polythene as the RHS suggests.

What survives where

Chives, lovage and mint are reliable to zone 3; lemon balm and French tarragon hold to zone 4. Thyme, oregano, sage and most lavenders are rated zone 5, with 'Phenomenal' lavender and creeping thyme reaching zone 4 under snow. Winter savory wants zone 6 unless sheltered. Every woody herb needs a dry, free-draining site – winter wet kills them long before cold does.

Rosemary indoors

Rosemary is rated zone 7, with 'Arp' and 'Madalene Hill' surviving zone 6 in a dry, sheltered spot. Everywhere colder it comes in, and most plants brought in during October are dead by February – from heat, darkness and overwatering, not thirst.

It wants a cool, bright winter rest at 5–10 °C (41–50 °F): a frost-free greenhouse, a glazed porch or a cold bright window. A 21 °C (70 °F) living room will not do – the plant keeps trying to grow without light to support it and gives up. Water every two to three weeks, only when the compost is dry well down, and give no feed between October and March.

Check the leaf undersides for spider mite before bringing it in, and move it back out gradually in April. Take cuttings in August as insurance – 8–10 cm (3–4 in) tips in gritty compost root in four to six weeks.

Zone table: sowing, planting out and winter care

Dates are for an average year. A north slope or an exposed site behaves like one zone colder, a sheltered south-facing wall like one zone warmer.

Direct sowing shifts six weeks between zone 7 and zone 3 while the cutting season shortens by as much. In zone 3 it is almost always right to start even dill and cilantro in deep pots and move the whole pot out, and the colder the zone, the more the herb garden belongs in containers and raised beds.

Common mistakes

• Planting Mediterranean and leafy herbs in one pot. One pot has one watering schedule, so one plant is always wrong.
• Feeding too much. Nitrogen gives thin leaves with little aroma and shoots that fail in winter. Half strength every three weeks in pots, one spring dressing in the ground.
• Watering a little and often. Mediterranean herbs dry out between waterings, leafy herbs want a deep soak.
• Cutting into the wood. Thyme, lavender, sage and rosemary do not resprout from grey stems. Cut only green growth, a third at most.
• Sowing dill and cilantro once. Both bolt within weeks. Sow a new short row every two weeks.
• Planting mint loose in a border. Use a pot, or a sunk pot with the rim above soil level.
• Keeping rosemary warm all winter. It wants 5–10 °C (41–50 °F), bright light and very little water.

Frequently asked questions

Which herbs are easiest for a beginner?
Chives, mint, thyme and dill. The first two are close to impossible to kill and return every year with no help. Thyme only asks that you do not overwater it, and dill germinates in a week and crops in six. Do not start rosemary or lavender from seed – buy plants instead.

Can you grow herbs indoors year round?
Yes, but only with a lamp. A south window is enough from April to September and not at all in November. Count on 12 hours of light a day. Chives, parsley, mint and basil do best inside; rosemary and thyme want a cooler winter rest than a heated room gives them.

How often should you water herbs in pots?
It depends on the group. Mediterranean herbs such as rosemary, thyme and lavender get water when the compost is dry 2–3 cm (1 in) down, often every five to seven days in July. Leafy herbs such as basil and parsley must never dry out and may need water daily in heat.

Why do supermarket herb pots always die?
They are forced hard in pure peat, hold far too many seedlings for the pot, and are meant to be used within weeks. To keep one going, cut it back by half, split the rootball, pot the seedlings on separately into real compost and give them the brightest spot you have.

Which herbs are perennial in zone 4?
Chives, mint and lovage are reliable, and lemon balm and French tarragon usually come through. Thyme, oregano, sage and lavender are rated zone 5, so in zone 4 they need a dry, sheltered site with snow cover or mulch; 'Phenomenal' lavender and creeping thyme are safer picks. Rosemary comes indoors.

Should you fertilise herbs?
Lightly, and far less than other crops. Nitrogen gives thin leaves with weaker aroma and shoots that will not survive winter. Perennials get one spring dressing, about 30 g per sq m (1 oz per sq yd), and herbs in pots half-strength liquid feed every three to four weeks. Stop by mid-July.

When should you harvest herbs for the best flavour?
Mid-morning, once the dew has dried but before the sun is high, and at the stage when flower buds show but have not opened. Essential oil content is highest then. Take no more than a third of a perennial at one time, and cut annuals back to 10–15 cm (4–6 in) so they regrow.

Can you freeze herbs instead of drying them?
Yes, and for soft-leaved herbs it is better. Basil, dill, parsley, chives, cilantro and tarragon lose almost all their flavour when dried but keep it frozen. Chop and freeze in ice cube trays with water or olive oil, about a tablespoon per cube, and use within a year. Drying suits thyme, oregano, sage and rosemary.

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